The electrostatic optical modulator employing a resilient electrode moving over a static electrode has been a subject of multiple patents and publications. The difference between these modulators originates essentially from the shape of electrodes involved as well as the direction and spatial limitations of movement of the flexible electrode relative to the static electrode, see e.g. U.S. Pat. Nos. 4,229,075; 4,208,103 and 4,786,149. Lateral membrane movement is used in optical shutter and display of U.S. Pat. No. 6,288,824, wherein the electrostatically moved membrane and static electrode consist of periodic metal stripes, so that lateral membrane movement opens or closes multiple slits to pass or shut the light. Another approach, see U.S. Pat. No. 6,600,474, relies on a flipping of the membrane by 180 degrees, and latching it at this position by an electrostatic force. No resilient force is applied, since the membrane freely turns around the hinges between two extreme positions.
Various examples of the electrostatic optical modulators are based on the field induced bending of a cantilever membrane which is moved toward a flat static electrode, thereby changing the optical state, see U.S. Pat. Nos. 3,553,364; 3,600,798; 4,229,732; 4,731,670 and 5,781,331. Another approach relies on an electrostatically induced twisting of the membrane mirror from its initial flat position to vary the optical reflection, see U.S. Pat. Nos. 3,746,911 and 4,710,732. This electrostatic optical modulator, known as Deformable Mirror Device (DMD), is currently commercially used in a projection display.
The DMD pixels represent a densely packed mirror array reflecting light beams into the objective lens when the pixels are unbiased (“on state”) and moving the reflected light out of the objective lens when they are electrostatically tilted ˜10 degrees (“off state”). The limitations of application of the DMD strictly to projection display originates from the small tilt of the twisted membrane, since 10 degree rotation is not enough to use the DMD pixels for the flat panel displays.
In the proposed shutter and display, according to the present invention, this limitation is lifted due to different pixel design which allows for membrane tilt of 90 degrees, thereby making it suitable for application to the flat panel displays.